Microcontroller with auto-alarm device

ABSTRACT

A microcontroller with a self-prompting (self-wake-up) device, particularly for use in electrical adjusting drives, having a control device for specifying an active and an inactive operating state to economize on supply power, contains an oscillator for emitting a prompting signal or a clock frequency. This oscillator is a low-frequency, power-saving oscillator. Provided in the microcontroller is a circuit, preferably a disconnectible phase-locking loop, which, from the low frequency of the oscillator, generates a substantially higher clock frequency for microcontroller core. The low-frequency oscillator is also integrated as an original component into the microcontroller. An undervoltage detection, whose output signal is able to be supplied directly to the microcontroller core, indicates undervoltage conditions immediately. Using a time-switch logic which monitors a non-operative time of the microcontroller core, the core is activated again via a prompting circuit. In the case of certain functions, it is also possible to work in a power-saving manner solely with the low frequency. Thus, a necessary buffer capacitance can be smaller.

FIELD OF THE INVENTION

The present invention relates to on a microcontroller having aself-prompting (self-wake-up) device, particularly for use in electricaladjusting drives.

BACKGROUND INFORMATION

In a known microcontroller having a self-prompting device, as describedin German Patent Application No. 4302 232, which is intended to be usedparticularly in electrical adjusting drives, it is provided with acontrol device for specifying an active and an inactive operating statein order to economize on supply power, as well as with an oscillator foremitting a prompting (wake-up) signal. This oscillator is providedoutside of the microcontroller and, has a relatively low clockfrequency. Besides the prompting of the microcontroller by an internalsignal emitted by the watchdog, the prompting is also possible atregular, periodically recurrent time intervals by the external promptingsignal supplied by the external oscillator and fed to the controlcircuit. The prompting takes place independently of the operating stateprevailing at the moment. The cycle of this external prompting signalshould be calculated in such a way that the microcontroller remains inthe inactive state as long as possible, in order to attain low averageenergy consumption. On the other hand, the cycle should be short enoughto be able to react sufficiently quickly to a changed operatingsituation, it being possible to communicate this via input lines.Therefore, if no internal prompting signal occurs in the meantime, thisknown microcontroller is always prompted in the rhythm of the externaloscillator.

SUMMARY OF THE INVENTION

A microcontroller with a self-prompting device having the characterizingfeatures has the advantage of making available a complete assembly, inwhich a low-frequency oscillator exhibiting low current consumption isintegrated into the microcontroller as well, and which, in the event thehigh-frequency clock-pulse source is not in operation, is advantageouslyable to supply and operate the microcontroller core with this low clockfrequency when there are few functions to be carried out. Consequently,an essential condition is created for it, namely that themicrocontroller can be operated in an energy-saving manner, and a buffercapacitor in the control electronics to be provided for emergency casescan be selected to be considerably smaller, and thus can be installed inthe control electronics as well.

According to the present invention, this is achieved in that theoscillator is a low-frequency oscillator, that provision is made in themicrocontroller for a circuit which, from the low frequency of thisoscillator, generates a substantially higher clock frequency for themicrocontroller core, that the oscillator is integrated as an originalcomponent into the microcontroller as well, and that provision is madefor an undervoltage detection circuit, whose output signal is able to besupplied directly to the microcontroller core.

According to one embodiment of the present invention, the circuit forgenerating the high clock frequency for the microcontroller core is adisconnectible phase-locking loop.

In another embodiment, the microcontroller of the present invention isprovided with a prompting circuit which, after a specific time haselapsed, or in response to the occurrence of a specific event, shiftsthe microcontroller core from the inactive into the active operatingstate.

In another embodiment, the microcontroller of the present invention isprovided with a time-switch logic which, after the expiration of avariably specifiable time span, acts upon the prompting circuit, so thatthe prompting circuit shifts the microcontroller core from the inactiveinto the active operating state.

In another embodiment of the present invention, the prompting signal ofthe prompting circuit activates that circuit which, from the lowfrequency of the low-frequency oscillator, generates the substantiallyhigher clock frequency for the microcontroller core, in order to shiftit from the inactive into the active operating state.

According to another embodiment of the present, the microcontroller ofthe present invention is provided with a multiplexer, via which themicrocontroller core, in certain operating situations, is able to bedirectly supplied with the frequency of the low-frequency oscillator asits clock frequency.

In advantageous manner, after executing particular functions, themicrocontroller core is able to be shifted into the inactive operatingstate for a specific time span which is adaptable to certaincircumstances. In another embodiment of the present invention, theadaptable time span is programmable and is able to be stored in atime-comparison register provided in the time-switch logic.

The microcontroller of the present invention is designed such that thefrequency of the low-frequency oscillator is, for example, 100 kHz, andthe frequency generated therefrom for the microcontroller core is, forexample, 10 MHz

The microcontroller according to the present invention is preferablyused for electrical adjusting drives of motor vehicles, and theundervoltage detection is connected directly to the electrical-systemvoltage, in order to detect undervoltage conditions without time delay.

BRIEF DESCRIPTION OF THE DRAWING

The FIGURE shows a block diagram of a microcontroller according to anexemplary embodiment of the present invention, having a self-prompting(self-wake-up) device.

DETAILED DESCRIPTION

Microcontroller 10, shown schematically in the FIGURE as a blockdiagram, contains a microcontroller core 11, a power-savinglow-frequency oscillator 12, a phase-locking loop 13, a multiplexer 14,a prompting circuit 15, a time-switch logic 16, as well as anundervoltage detection circuit 17 as essential components. In addition,a power supply 18 and an input/output circuit 19 are also shown in theblock diagram.

Microcontroller core 11 is used to fulfill the tasks of microcontroller10, and is operated with a specific clock frequency. For example, thisclock frequency can be 10 MHz, if the clock pulse is supplied fromphase-locking loop 13 via line 20. Phase-locking loop 13 generates thishigh clock frequency from low-frequency signals which are supplied online 21 from low-frequency oscillator 12. For example, the frequency ofoscillator 12 can be 100 kHz. Thus, phase-locking loop 13, for whichpreferably a PLL circuit (phase-locked loop circuit) is used, representsa circuit which generates a substantially higher clock frequency formicrocontroller core 11 from the low frequency of oscillator 12. In thiscontext, the phases of low and high clock frequency are in regulated,fixed relation to one another. The complete PLL circuit is disconnectedin the inactive operating state since, because of the high frequency, itneeds a high operating current.

Multiplexer 14, provided in microcontroller 10, receives the high clockfrequency of phase-locking loop 13 via line 20, or the low frequency oflow-frequency oscillator 12 via line 21. Time-switch logic 16 is drivenvia an output line 23, and is provided either with the high or the lowclock frequency. Furthermore, a control signal is supplied frommicrocontroller core 11 via a line 24 to multiplexer 14. Time-switchlogic 16 is in bidirectional signal exchange via line 25 withmicrocontroller core 11, and gives a signal via an output line 26 toprompting circuit 15. Prompting circuit 15 acts with its promptingsignal, via an output line 27, upon microcontroller core 11, in order tobring microcontroller core 11 from the inactive into the activeoperating state. This takes place after a specific elapsed time span,which is determined during the active phase of microcontroller core 11,and is set via line 25 in a register in time-switch logic 16. Suppliedwith clock signals via multiplexer 14 and line 23, time-switch logic 16monitors and compares the set time inputs. At the predetermined point oftime, prompting circuit 15 is then driven via line 26.

Microcontroller core 11 is connected via an input line 28 and an outputline 29 to input/output circuit 19. Illustratively, microcontroller core11 is supplied with and acted upon by signals via this circuit which,e.g., come from the keyboard (e.g. data acquisition), relay drivers,positional-signal transmitters and other relevant and connected modules,and which are input via input line 28. Conversely, these modules aresupplied via output line 29 with control and other signals by way ofinput/output circuit 19.

Following, important functions of microcontroller 10 according to thepresent invention are clarified in the light of the application ofmicrocontroller 10. Position detection with the assistance ofincremental encoders is employed for electrical adjusting drives inmotor vehicles. Hall-effect sensors, for example, can be used for thatpurpose. Such drives having position detection are in use, e.g., forelectrical window lifters with anti-squeeze or finger protection,sunroof drives and seat-adjustment systems with memory function. Forsuch systems, the position detection should still be realizable, evenafter an emergency shutdown because of low voltage, particularly due todisconnect of the battery or the blowing of a vehicle fuse during theadjustment operation. The after-running time of a typical adjustingmotor can be up to 100 ms. Since the position data must subsequentlystill be written into a non-volatile storage, the system ofmicrocontroller plus sensors must be supplied from a capacitance forbuffer times (or data-support times) of approximately 120 ms.

The minimal electrical-system voltage at which the drives are stilldriven is usually 9 V. A voltages of approximately 1.2 V for thepolarity-reversal diode and the voltage drop at a voltage regulator areprovided. The minimal functional voltage for Hall-effect sensors, whichare used for position detection, and the microcontroller lies atapproximately 3.8 V. Resulting from this is a permissible voltage dropin the buffer capacitance of

ΔU=9 V−1.2 V−3.8 V=4 V.

Thus, assuming 30 mA total current consumption for this system, aminimum magnitude of is yielded for the buffer capacitance.$C = {\frac{{I \cdot \Delta}\quad t}{\Delta \quad U} = {\frac{30\quad {{mA} \cdot 120}\quad {ms}}{4\quad V} = {900\quad {µF}}}}$

is yielded for the buffer capacitance.

Because of their large dimensions, capacitors of this capacitance canonly be integrated with great difficulty into the customarymotor-control electronics.

To reduce the average current consumption of the system, themicrocontroller and Hall-effect sensors are switched in only for a timeto sample the sensor level. Microcontroller 10 of the present inventionmeets the following requirements for this purpose:

it has a power-saving, inactive operating state (power down mode);

the start-up time of microcontroller 10 is perceptibly less than thesampling-time interval to be expected;

microcontroller 10 contains an undervoltage detection 17 which, forexample, is directly connected as threshold-value acquisition to theelectrical-system voltage, and thus detects the undervoltage conditionwithout time delay and communicates this condition via line 30 tomicrocontroller core 11;

finally, with the expiration of a specific time after entering into theinactive operating state, or in response to the occurrence of a specificevent, the microcontroller is shifted again into the active operatingstate by its self-prompting device.

If, in microcontroller 10 configured according to the present invention,it is determined in undervoltage detection circuit 17 that theelectrical-system voltage has fallen below a minimum level, thefollowing actions are carried out:

the position signals of the Hall-effect sensors are evaluated; theHall-effect sensors are disconnected;

the desired time span for the inactive operating state is determined,and this value is set as comparison value in the register in thetime-switch logic;

the system clock pulse is changed over from phase-locking loop 13 tolow-frequency oscillator 12; finally, microcontroller core 11 isstopped, i.e., microcontroller 10 is shifted into the inactive operatingstate (stop mode).

During the inactive operating state, time-switch logic 16 is suppliedwith the low-frequency clock pulse. This is taken into account whencalculating the value for the inactive time span which is input into theregister, so that the correct prompting (wake-up) time can be achieved.When the time span for the inactive operating state has elapsed,prompting circuit 15, initiated by a signal on line 26 of time-switchlogic 16, will generate a prompting signal for microcontroller core 11,and supply it to microcontroller core 11 said core via line 27. Theprompting signal causes phase-locking loop 13 to be activated. After thetransient recovery time of phase-locking loop 13 of, e.g., approximately200 μs has elapsed, microcontroller core 11 is fully functional.

If, within the active operating state, the running phase ofmicrocontroller 10, only a few functions are carried out, e.g., theevaluation of the position signals of Hall-effect sensors, then with theassistance of appropriately controlled multiplexer 14, microcontrollercore 11 is supplied only with the low-frequency clock pulse on outputline 21 of low-frequency oscillator 12. In this case, phase-locking loop13 does not have to be activated, and the associated transient recoverytime is saved. Microcontroller core 11 is ready for operationimmediately after receiving the prompting signal, but operates with thelower clock frequency. When the tasks are executed, the time span forthe inactive operating state is determined anew, set in the register oftime-switch logic 16, and the microcontroller shuts itself down for thistime span.

The present invention provides a specially configured microcontrollerhaving a self-prompting device in which, by switching into the activeoperating state for only brief periods, the average current consumptionis advantageously reduced corresponding to the ratio of running time tonon-operative time. Consequently, the buffer capacitance necessary forthe case of emergency shutdown in response to undervoltage is reduced.The microcontroller can be operated both with high and with lowfrequency. During the inactive operating state, the clock pulse of thepower-saving, low-frequency oscillator, which is also integrated intomicrocontroller 10, is made available.

What is claimed is:
 1. A microcontroller for an electrical adjustingdrive, comprising: a microcontroller core setting an active operatingstate and an inactive operating state of the microcontroller to conservea supply power; a prompting circuit generating a prompting signal to themicrocontroller core for switching the microcontroller from the inactiveoperating state to the active operating state after a predetermined timeperiod or in response to an occurrence of a predetermined event; alow-frequency oscillator providing a basic clocking function andgenerating an oscillator signal which has a first clock frequency, thelow-frequency oscillator being an original component of themicrocontroller; a further circuit generating, as a function of theoscillator signal, a circuit signal for the microcontroller core, thecircuit signal having a second clock frequency which is higher than thefirst clock frequency; an undervoltage detection circuit generating anoutput signal which is provided directly to the microcontroller core,wherein, if the undervoltage detection circuit determines that a voltageis below a predetermined level: the microcontroller core evaluatesposition signals of position sensors and disconnects the positionsensors, a first arrangement determines the predetermined time period, asecond arrangement changes a system clock pulse from the circuit signalhaving the second clock frequency to the oscillator signal having thefirst clock frequency, and the microcontroller is switched into theinactive operating state.
 2. The microcontroller according to claim 1,wherein, after an activation phase and before the prompting circuitgenerates a next prompting signal, the microcontroller core disconnectsthe microcontroller using an automatic shutdown procedure.
 3. Themicrocontroller according to claim 1, wherein the undervoltage detectioncircuit detects at least one of a sudden voltage drop and a gradualvoltage drop, and wherein the microcontroller core switches themicrocontroller from the active operating state to the inactiveoperating state based on one of the sudden voltage drop and the gradualvoltage drop.
 4. The microcontroller according to claim 1, wherein thefurther circuit includes a disconnectable phase-locking looparrangement.
 5. The microcontroller according to claim 1, wherein thefirst arrangement includes a time-switch logic arrangement, and wherein,after the predetermined time period, the time-switch logic arrangementacts on the prompting circuit to generate the prompting signal to themicrocontroller core for switching the microcontroller from the inactiveoperating state to the active operating state.
 6. The microcontrolleraccording to claim 5, wherein the prompting signal activates the furthercircuit, the further circuit generating the circuit signal as a functionof the oscillator signal, the microcontroller core switching themicrocontroller from the inactive operating state to the activeoperating state using the second clock frequency.
 7. The microcontrolleraccording to claim 1, wherein the second arrangement includes amultiplexer, the multiplexer providing the oscillator signal to themicrocontroller core to set a frequency of the microcontroller coreequal to the first clock frequency.
 8. The microcontroller according toclaim 5, wherein the time-switch logic arrangement determines thepredetermined time period, and wherein the time-switch logic arrangementincludes a time-comparison register for storing the predetermined timeperiod.
 9. The microcontroller according to claim 1, wherein thelow-frequency oscillator generates the oscillator signal having thefirst clock frequency equal to 100 kHz, and wherein the microcontrollercore receives the circuit signal having the second clock frequency equalto 10 MHZ.
 10. The microcontroller according to claim 1, wherein theundervoltage detection circuit is connected directly to anelectrical-system voltage of the electrical adjusting drive fordetecting undervoltage conditions without a time delay and for providingthe undervoltage conditions to the microcontroller core, the electricaladjusting drive being provided in a motor vehicle.